With manually powered weapons, such as an archery bow, that are inherently more difficult to aim, one of the difficulties faced by an archer is determining how high or low to aim when attempting to hit a target. This decision is further complicated when the target is below the archer (as when hunting animals from a tree stand) or when the target is above the archer (as when an animal is on a hill). This decision becomes further complicated when the target is an animal that moves away from or towards the archer. As a result, a variety of bow sights have been developed to aid the archer to accurately aim at the target.
One type of bow sight employs a series of sighting pins calibrated to different distances. This type of sight arrangement only provides accurate sighting at the discreet interval defined by the various pins. For example, the sight arrangement might require the archer to utilize the first pin when the target is ten yards from the archer, the second pin when the target is twenty yards from the archer, and so on as the target's distance from the archer increases. This type of arrangement is inconvenient, as an archer must use a different pin or cross hair for targets at different distances. Furthermore, an archer has to determine which pin to use prior to making the shot. Furthermore, since the sights are calibrated for particular distances, the hunter must estimate the distance to the target and use the pin calibrated to that distance to sight the target. These sights also require the hunter to approximate when the target is at a distance between one of the calibrated distances. Furthermore, these sighting arrangements are designed for use when the archer and the target are at substantially the same elevation. Because the fixed pin sight arrangement assumes the angle of the bow, the pins are no longer calibrated for the same distances as a ground level shot when the archer is elevated above the target or visa versa. Thus, these arrangements tend to be limited to uses when the archer and the target are on the same elevation.
Attempts to overcome the limitations of shooting to different elevations have resulted in pendulum type sighting devices that pivot relative to the bow. These sights tend to position a cross hair or sight pin along an arc defined by the distance between the pin or cross hair to the pivot point. While these pendulum sights can aid the archer for aiming at either a target above or a target below the archer, they do not accurately sight for both. A pendulum bow sight for use at both elevated and ground level positions tends to have at least two sets of cross hairs or sight pins, one pendulum and one stationary, in order to effectively sight at both positions. None of these devices have adequately resolved the problem of providing continuous sighting with a single sight element while compensating for both elevation and range of the target with respect to the archer.